Fingerprint imaging recognition technology is used to realize identification by capturing fingerprint images of a person using optical fingerprint sensors or modules and then determining whether the fingerprint image information matches that already stored in a system. Due to its convenience in use and uniqueness of human fingerprints, the fingerprint recognition technology has been widely applied to various fields, such as security inspection field including Public Security Bureau (PSB) or the like, access control systems of buildings, consumption goods field including personal computers or mobile phones etc., and the like. The fingerprint recognition technology may be realized by optical imaging, capacitance imaging, ultrasound imaging and the like, among which, the optical fingerprint recognition technology is advantageous in the imaging quality and device cost.
As shown in FIG. 1, an existing optical fingerprint module includes a backlight source 110, an optical fingerprint sensor 120, a protective layer 130 and a shell (not shown in FIG. 1). When a fingerprint image is captured, a finger 140 of a person is placed on the protective layer 130. An output light 111 of the backlight source 110 (upward arrows in FIG. 1 represent the output light 111, as enclosed in a dotted line frame) passes through the optical fingerprint sensor 120 and the protective layer 130, and is reflected and transmitted at a contact interface between the finger 140 and the protective layer 130. The reflected light 112 (downward arrows in FIG. 1 represent the reflected light 112, as enclosed in a dotted line frame) passes through the protective layer 130 and irradiates onto the optical fingerprint sensor 120. The optical fingerprint sensor 120 performs photoelectric conversion and signal processing by its inner circuits (not shown in FIG. 1) to realize fingerprint image capturing. Since characteristics of a contact interface between the finger 140 and the protective layer 130 reflect fingerprint characteristics of the finger, and the characteristics of the contact interface directly affect characteristics of the reflected light 112, the image captured by the optical fingerprint sensor 120 shows the fingerprint characteristics of the person.
More information on optical fingerprint modules may refer to the Chinese Utility Model Patent with a publication No. CN105184230A and a publication date of Dec. 23, 2015.
However, structures and performance of the existing optical fingerprint modules still remain to be improved.